Paraneoplastic Secretion of Multiple Phosphatonins from a Deep Fibrous Histiocytoma Causing Oncogenic Osteomalacia

This data describes the first case of oncogenic osteomalacia due to a plexiform fibrohistiocytic tumor which coincidentally has been found for the first time to induce profound muscle weakness via the overexpression of three phosphatonins which resolved fully upon radical resection of the tumor. Much of the literature suggests that oncogenic osteomalacia is usually caused by a benign mesenchymal tumor secreting fibroblast growth factor subtype-23 (FGF23) but other phosphatonins are rarely implicated.We have previously reported a seemingly typical case of oncogenic osteomalacia. Following curative neoplasm resection, we now report unique molecular characteristics and biology of this tumor never described before. A 25-year-old man had been diagnosed with severe oncogenic osteomalacia that gradually crippled him over 6 years. 68Ga-DOTA-TATE PET-CT scan localized the culprit tumor to his left sole which on resection revealed a plexiform fibrohistiocytic tumor positive for CD34 and CD163 with osteoclast-like giant cells and scattered stromal dendritic cells within the tumor. Circulating FGF23 which was elevated more than 2-folds declined to undetectable levels 24 hours after surgery. Microarray analysis showed over 150-fold upregulation in FGF23, matrix extracellular phosphoglycoprotein (MEPE) and secreted frizzled-related protein subtype 4 (sFRP4) genes which corresponded to the same proteins overexpressed on Western blots Total RNA was obtained from a total of six samples, which consisted of three pairs of technical replicates each for tumour, adjacent and skin samples